Extractability testing sodium carbonate solution extractant

To a mixture of 10 g. of the compound and 3-5 ml. of 33 per cent, sodium hydroxide solution in a test-tube, add 2-5 ml. of 50 per cent, chloroacetic acid solution. If necessary, add a little water to dissolve the sodium salt of the phenol. Stopper the test-tube loosely and heat on agently-boiling water bath for an hour. After cooling, dilute with 10 ml. of water, acidify to Congo red with dilute hydrochloric acid, and extract with 30 ml. of ether. Wash the ethereal extract with 10 ml, of water, and extract the aryloxyacetic acid b shaking with 25 ml. of 5 per cent, sodium carbonate solution. Acidify the sodium carbonate extract (to Congo red) with dilute hydrochloric acid, collect the aryloxyacetic acid which separates, and recrystallise it from hot water. 

The checkers found it convenient to test the pH of the extract with Hydrion papers. When the pH of the extract became the same as that of the saturated sodium carbonate solution, the color of the extract changed from green to orange Thereafter, extraction was continued until neutralization of small aliquots with concentrated hydrochloric acid produced no solid. 

Qualitative Tests.—The solution of this extract is yellow and with acids becomes paler and then gives a yellow precipitate, whilst with alkalies it becomes darker and gives an orange-brown precipitate. The solution also gives a yellow precipitate with stannous chloride, a deep olive green precipitate with ferric chloride and a pale yellow precipitate with alum and then a few drops of sodium carbonate solution. With chloride of lime it first turns brown and then colourless, a brownish-yellow precipitate settling. 

Phenylacetic acid. Into a 500-ml round-bottomed flask, provided with a reflux condenser, place 100 ml of water, 100 ml of concentrated sulphuric acid and 100 ml of glacial acetic arid add lOOg (98 ml, 0.85 mol) of benzyl cyanide. Heat under reflux for 45-60 minutes hydrolysis is then complete. Pour the mixture into 2-3 volumes of water with stirring. Filter the crude arid at the pump. Melt the crude material under water, and wash it two or three times with small volumes of hot water the acid solidifies on cooling. Test a small portion for the presence of phenylacetamide (m.p. 155 °C) by dissolving in sodium carbonate solution. If a clear solution results, phenylacetamide is absent if the solution is not clear, shake the whole of the crude product with excess of sodium carbonate solution, filter and precipitate the phenylacetic arid from the clear filtrate by the addition of dilute sulphuric arid. Filter off the phenylacetic acid and recrystallise it from hot water or, better, light petroleum (b.p. 40-60 °C). The yield of pure acid, 77 °C, is 50 g (43%). Small quantities of acid may be recovered from the mother-liquors by extraction with ether, but this is rarely worth while. Alternatively the acid may be purified by distillation under reduced pressure, b.p. 140-150 °C/20mmHg. The p.m.r. spectrum should be recorded and compared with that shown in Fig. 3.47. The 13C-n.m.r. spectrum is shown in Fig. 3.55. 

Test for iodide in the neutralized soda extract or in a solution of the sodium salts by the addition of a few drops of chlorine water (or acidified sodium hypochlorite solution) and 2-3 ml chloroform or carbon tetrachloride the latter is coloured violet. Add excess silver sulphate solution to another portion of the neutral solution and filter off the silver iodide remove the excess silver sulphate with sodium carbonate solution. Pass sulphur dioxide into the filtrate to reduce iodate to iodide, boil off the excess sulphur dioxide, and add silver nitrate solution and dilute nitric acid. A yellow precipitate of silver iodide confirms the presence of iodate in the original substance. 

Thiosulphate will be detected in the preliminary test with dilute sulphuric acid if it is found, it should be eliminated by heating the original mixture with dilute sulphuric acid until no more sulphur dioxide is evolved, evaporating the residual mixture just to dryness and then heating with 1-5m sodium carbonate solution, etc. The occurrence of thiosulphates in mixtures is comparatively rare and hence this special treatment prior to making the soda extract is rarely necessary. The interference of the S2Of ion with the silver nitrate reaction may... 

It is not possible to devise a comprehensive separation scheme for anions however, it is possible to detect them individually in most cases, after perhaps a 1-2 stage separation. It is advantageous to remove all heavy metals from the sample by extracting the anions through boiling with sodium carbonate solution heavy metal ions are precipitated out in the form of carbonates, while the anions remain in solution accompanied by sodium ions. The selected tests are listed in order of increasing complexity it is advisable to do them in the order they are described. 

Procedure A drop of the neutral or acid test solution is treated successively in a micro test tube with four drops of the reagent solution, one drop of a 10% sodium hydroxide solution and one drop of 10% sodium carbonate solution and extracted with 3-4 drops of chloroform. Addition of a few drops of water hastens the separation of the two layers. A red color in the CHCI3 layer indicates the presence of calcium. When testing for small amounts of calcium a blank test is advisable. 

Shake the vessel containing the test extractant vigorously. Obtain a suspension of Santonox in 5% w v sodium carbonate solution, and immediately measure 44.1 ml of the extractant and transfer to a 100 ml volumetric flask. Slowly add 7 ml of glacial acetic acid and allow the effervescence to subside. Dilute to 100 ml with ethanol. 

Prepare a blank solution in a similar manner by adding glacial acetic acid and ethanol in the previous proportions to a 5% wiv sodium carbonate solution. Use this solution in the 1 cm reference cell of the spectrophotometer and measure the optical density of the test extractant at 250 nm versus the blank in the reference cell. 

To isolate the product from its toluene solution, the toluene solution is extracted with several portions of a 10% solution of sodium carbonate in water until the acidification of a test portion of the aqueous extract shows that no more nitro ester is being extracted by the sodium carbonate solution. 

Benzoates. Dissolve 0-5 g. of the amino acid in 10 ml. of 10 per cent, sodium bicarbonate solution and add 1 g. of benzoyl chloride. Shake the mixture vigorously in a stoppered test-tube remove the stopper from time to time since carbon dioxide is evolved. When the odour of benzoyl chloride has disappeared, acidify with dilute hydrochloric acid to Congo red and filter. Extract the solid with a little cold ether to remove any benzoic acid which may be present. RecrystaUise the benzoyl derivative which remains from hot water or from dilute alcohol. 

This solution may also be employed in the test for bromine. If iodine has been found, add small amounts of sodium nitrite solution, warm shghtly and shake with fresh 1 ml. portions of carbon tetrachloride until the last extract is colourless boil the acid solution until no more nitrous fumes are evolved and cool. If iodine is absent, use 1 ml. of the fusion solution which has been strongly acidified with glacial acetic acid. Add a small amount of lead dioxide, place a strip of fluorescein paper across the mouth of the tube, and warm the solution. If bromine is present, it will colour the test paper rose-pink (eosin). 

It is recommended that the eompound be fused with a mixture of sodium carbonate (2 parts) and sodium peroxide (1 part) as in the test for Plvoaphoms. Extract the fused mass with water, filter, and acidify with dilute hydrochloric acid. Pass hydrogen sulphide through the hot solution arsenic is precipitated as yellow arsenic sulphide. If antimony is present, it will be precipitated as orange antimony trisulphide. 

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